A palm-sized "robo-bat" with shape memory alloy jointed limbs and smart
material alloy muscles is being built by North Carolina State
University researchers. It's the perfect micro air vehicle (MAV) for
surveillance or other kinds of data gathering — Batman could fit this
gadget easily onto his utility belt.

Gheorghe Bunget, a doctoral student in mechanical engineering at
NC State, and his advisor Dr. Stefan Seelecke looked to nature for
inspiration. "We are trying to mimic nature as closely as possible,"
Seelecke says, "because it is very efficient. And, at the MAV scale,
nature tells us that flapping flight – like that of the bat – is the
most effective."

According to the NC State press release, the fully assembled robotic
'bat' skeleton rests easily in the palm of your hand and, at less than
6 grams, feels as light as a feather.

The research team is using a special shape memory alloy that is
super-elastic for the joints of the robo-bat. The material offers a
full range of motion, but always returns to its original gliding
position. These materials have many uses; it is even possible to make a
'soft' robot powered by shape memory alloy spokes.

Smart materials are also being used for the 'muscles' on the robotic bat. Seelecke explains:

"We're using an alloy that responds to the heat from an electric
current. That heat actuates micro-scale wires the size of a human hair,
making them contract like 'metal muscles.' During the contraction, the
powerful muscle wires also change their electric resistance, which can
be easily measured, thus providing simultaneous action and sensory
input. This dual functionality will help cut down on the robo-bat's
weight, and allow the robot to respond quickly to changing conditions –
such as a gust of wind – as perfectly as a real bat."

It's interesting that science fiction writers also chose to mimic
nature in the earliest descriptions of robotic MAVs. I was thinking in
particular about the extraordinary Scarab flying insect robot from
Raymond Z. Gallun's The Scarab, published in Astounding Stories magazine in 1936.

"The Scarab rubbed its hind legs together, as flies will do
when at rest. Then, apparently satisfied that it was in condition, it
unfolded the coleoptera-like plates over its wings. With a buzz that
any uninformed person would have mistaken for that of a beetle, it
started out on its journey." (Read more about the scarab flying insect robot)

For a different take on the idea of a robotic bat by a different research team, take a look at the COM-BAT Robotic 'Bat' On Order From UM . The development process for this tiny MAV emphasizes the senses of a robotic bat.